[PATCH 6/9] use IO#wait_readable consistently

[Eric Wong <e@80x24.org>]

Since Ruby 2.3, it no longer checks FIONREAD, and we require
Ruby 2.3+ nowadays, so drop our IO.select-based workarounds.
---
 bin/dtas-readahead      | 16 ++--------------
 lib/dtas/unix_client.rb |  4 ++--
 2 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/bin/dtas-readahead b/bin/dtas-readahead
index d3c6e79..75bfbe8 100755
--- a/bin/dtas-readahead
+++ b/bin/dtas-readahead
@@ -28,18 +28,6 @@
 @redir = { err: null, out: null, in: null }.freeze
 require 'pp'
 
-if RUBY_VERSION.to_r >= '2.3'.to_r
-  # Old Rubies did FIONREAD, which breaks on SOCK_SEQPACKET
-  def wait_read(w, timeout)
-    w.to_io.wait_readable(timeout)
-  end
-else
-  def wait_read(w, timeout)
-    r = IO.select([w], nil, nil, timeout)
-    r ? r[0] : nil
-  end
-end
-
 def seek_to_cur_pos(cur_pid, fp)
   cur_fd = []
   fpst = fp.stat
@@ -120,7 +108,7 @@ def do_ra(fp, pos, w)
     len -= n
 
     # stop reading immediately if there's an event
-    if wait_read(w, 0)
+    if w.to_io.wait_readable(0)
       adj = @todo_ra
       pos += size
       break
@@ -220,7 +208,7 @@ def do_open(path)
     fp.close if fp && !fp.closed?
     fp = timeout = nil
   end
-  r = wait_read(w, timeout)
+  r = w.to_io.wait_readable(timeout)
   p w.res_wait if r
 rescue EOFError
   abort "dtas-player exited"
diff --git a/lib/dtas/unix_client.rb b/lib/dtas/unix_client.rb
index 8aa953c..71f833c 100644
--- a/lib/dtas/unix_client.rb
+++ b/lib/dtas/unix_client.rb
@@ -1,4 +1,4 @@
-# Copyright (C) 2013-2020 all contributors <dtas-all@nongnu.org>
+# Copyright (C) all contributors <dtas-all@nongnu.org>
 # License: GPL-3.0+ <https://www.gnu.org/licenses/gpl-3.0.txt>
 # frozen_string_literal: true
 require_relative '../dtas'
@@ -39,7 +39,7 @@ def req(args, timeout = nil)
   end
 
   def res_wait(timeout = nil)
-    IO.select([@to_io], nil, nil, timeout)
+    @to_io.wait_readable(timeout)
     nr = @to_io.nread
     nr > 0 or raise EOFError, "unexpected EOF from server"
     @to_io.recv(nr)